Horologium is a faint constellation in the southern sky. Covering a total of 248.9 square degrees or 0.603% of the sky, Horologium ranks 58th in area out of the 88 modern constellations. Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 23°N. Horologium is bordered by five different constellations: Eridanus (the Po River), Caelum (the chisel), Reticulum (the reticle), Dorado (the dolphinfish/swordfish), and Hydrus (the male water snake). In the equatorial coordinate system, the right ascension coordinates of the constellation lie between 02h 12.5m and 04h 20.2m, while the declination coordinates are between −39.63° and −67.04°.
Horologium, shown as Horologium Pendulum, in the Uranographia of Johann Bode (1801)
[http://www.ianridpath.com/startales/horologium.htm]
The French astronomer Nicolas Louis de Lacaille first described the constellation in 1752, after he had observed and catalogued almost 10,000 southern stars during a two-year stay at the Cape of Good Hope. He devised fourteen new constellations in uncharted regions of the Southern Celestial Hemisphere not visible from Europe. All but one honored instruments that symbolized the Age of Enlightenment Lacaille Latinized the name to Horologium on his 1763 chart.
[http://www.davidmalin.com/fujii/source/afn1-04.html]
[http://www.dibonsmith.com/graphs_SH.htm]
Alpha Horologii
[http://informationaboutstars.com/starinfo.dc/star/id-216710/]
Alpha Horologii is the only one star brighter than apparent magnitude 4. It is an orange giant star located 115 light-years from Earth. It shines with a luminosity approximately 37.61 times that of the Sun and has a surface temperature of 5028 K.
[https://en.wikipedia.org/wiki/Alpha_Horologii]
Light Curve of R Hor (R Horologii) from the AFOEV database (1900-1999)
[http://www.kusastro.kyoto-u.ac.jp/vsnet//AFOEV/LCs/index/HORR.html]
R Horologii (also known as HD 18242) is a red giant star approximately 700 light-years away. It is also a Mira variable with a period of 404.83 days, and ranging from apparent magnitude 4.7 to 14.3- one of the largest ranges in brightness known.
[https://en.wikipedia.org/wiki/R_Horologii]
Beta Horologii is the third-brightest star in the constellation of Horologium. It is an A-type giant star with an apparent visual magnitude of approximately 4.979, and is a chemically peculiar star of the metallic-line type.
[https://en.wikipedia.org/wiki/Beta_Horologii]
Gliese & Jahreiss 1061
[https://jumk.de/astronomie/near-stars/gliese-jahreiss-1061.shtml]
Gliese 1061 is a type of star known as a red dwarf, located just 12 light-years from Earth in the southern constellation of Horologium. Even though it is a relatively nearby it has an apparent visual magnitude of about 13 so it can only be seen with at least a moderately-sized telescope.
The proper motion of Gliese 1061 has been known since 1974, but it was estimated to be further away: approximately 25 light years distant based upon an estimated parallax of 0.130″. Its distance was only accurately determined in 1997 by the RECONS team. At that time it was the 20th nearest star system to the Sun. The discovery team noted that many more stars such as this are likely to be discovered nearby.
This star is a very small, dim, red dwarf, close to the lower mass limit for a star. It has an estimated mass of about 11.3% of the Sun and is only 0.1% as luminous. The star has been examined for the presence of an astrometric companion, but none has been detected. Nor does it display a significant infrared excess due to circumstellar dust.
[https://en.wikipedia.org/wiki/Gliese_1061]
Iota Horologii
Iota Horologii is a yellow dwarf star approximately 56 light-years away in the Horologium constellation. The star is classified as a G0V yellow dwarf. It has a mass and radius larger than the Sun, and is about 50% more luminous.
In 1999, a planet of the star was discovered. Because the planet orbits in a near Earth orbit, Iota Horologii was ranked 69th in the list of candidates for NASA’s planned Terrestrial Planet Finder mission. In 2000, a dust disc was announced around the star, but this was later determined to be an instrumental artifact.
Since Iota Horologii is in the minor constellation of Horologium and is quite dim in the sky, it has not been given a traditional name. It lies roughly between the stars Eta Horologii and R Horologii (though it is not close to them in real space).
In its current position, Iota Horologii is closest to the star Chi Eridani (a yellow subgiant), approximately 7 light-years away. The closest planetary systems to Iota Horologii are HD 10647 (a yellow dwarf), approximately 57 light-years away, and Epsilon Reticuli (an orange subgiant), approximately 59 light-years away. Other star systems close to Iota Horologii include Nu Phoenicis and Zeta Reticuli.
Spectrographic analysis indicates the star must have formed together with the stars of the Hyades cluster (~625 million years ago) but must have slowly drifted away, being presently more than 130 light-years away from its original birthplace. This also means that the amount of metals present in the star is due to the original cloud from which it formed and not because it engulfed planetary material.
Measurements of magnetic activity with the 1.5 m telescope at Cerro Tololo Inter-American Observatory show that the star has a 1.6 year magnetic activity cycle which is the shortest cycle measured so far for a solar like star. The sun by comparison has an 11-year magnetic activity cycle.
[https://en.wikipedia.org/wiki/Iota_Horologii]
NGC 1261 from Hubble Legacy Archive
There are several globular clusters in the constellation. NGC 1261 is a globular cluster of 8th magnitude, located 44,000 light-years from Earth.
Globular cluster Arp-Madore 1
Arp-Madore 1 is a globular cluster visible in the constellation Horologium, located 398,000 light-years away. It is one of the most distant known globular clusters of the Milky Way galaxy’s halo; its distance gives it interest as a test case for gravitational theories. It is named after Halton Arp and Barry F. Madore, who identified it as a distant globular cluster in 1979, using the UK Schmidt Telescope, after previous researchers at the European Southern Observatory had observed its existence but not its classification.
[https://en.wikipedia.org/wiki/Arp-Madore_1]
The inner ring of NGC 1512 as imaged by the Hubble Space Telescope (HST)
NGC 1512 is a barred spiral galaxy approximately 38 million light-years away from Earth in the constellation Horologium. The galaxy displays a double ring structure, with one ring around the galactic nucleus and another further out in the main disk. NGC 1512 is a member of the Dorado Group.
[https://en.wikipedia.org/wiki/NGC_1512]
NGC 1433 is a barred spiral galaxy with a double ring structure located in the constellation of Horologium. It has an active galactic nuclei, and it is also known as Miltron’s Galaxy. The central region of the galaxy portraits intense star formation activity, with an irregular star-forming ring of 5" (or 0.3 kpc) radius and weak radio wave emission. Star formation is also noticeable in the spiral arms but not the bar of the galaxy. NGC 1433 is being studied as part of a survey of 50 nearby galaxies known as the Legacy ExtraGalactic UV Survey (LEGUS). A jet of material flowing away from the central black hole of the galaxy extending for only 150 light-years has been found:
[https://en.wikipedia.org/wiki/NGC_1433]
A galaxy with a glowing heart
This view, captured by the NASA/ESA Hubble Space Telescope, shows a nearby spiral galaxy known as NGC 1433. At about 32 million light-years from Earth, it is a type of very active galaxy known as a Seyfert galaxy- a classification that accounts for 10% of all galaxies. They have very bright, luminous centers comparable to that of our galaxy, the Milky Way.
Galaxy cores are of great interest to astronomers. The centers of most, if not all, galaxies are thought to contain a supermassive black hole, surrounded by a disc of infalling material.
NGC 1433 is being studied as part of a survey of 50 nearby galaxies known as the Legacy ExtraGalactic UV Survey (LEGUS). Ultraviolet radiation is observed from galaxies, mainly tracing the most recently formed stars. In Seyfert galaxies, ultraviolet light is also thought to emanate from the accretion discs around their central black holes. Studying these galaxies in the ultraviolet part of the spectrum is incredibly useful to study how the gas is behaving near the black hole. This image was obtained using a mix of ultraviolet, visible, and infrared light.
LEGUS will study a full range of properties from a sample of galaxies, including their internal structure. This Hubble survey will provide a unique foundation for future observations with the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/submillimeter Array (ALMA). ALMA has already caught unexpected results relating to the center of NGC 1433, finding a surprising spiral structure in the molecular gas close to the center of NGC 1433. The astronomers also found a jet of material flowing away from the black hole, extending for only 150 light-years — the smallest such molecular outflow ever observed in a galaxy beyond our own.
[https://www.spacetelescope.org/images/potw1427a/]
A map of the Horologium Supercluster
The Horologium Supercluster, also known as Horologium-Reticulum Supercluster, consisting of SCl 48 and SCl 49 is a massive supercluster; spanning about 550 million light-years, it has a mass of 10^17 solar masses, similar to that of the Laniakea Supercluster that houses the Milky Way. It is centered on coordinates right ascension 03h 19m and declination −50° 02′, and spans an angular area of 12° × 12°.
The nearest part of the supercluster is 700 million light-years (z=0.063) away from Earth, while the far end of it is 1.2 billion light-years, visible in the constellations Horologium and Eridanus. The Horologium Supercluster has about 5,000 galaxy groups (30,000 giant galaxies and 300,000 dwarf galaxies). It includes the cluster Abell 3266.
[https://en.wikipedia.org/wiki/Horologium_Supercluster]
[https://en.wikipedia.org/wiki/Horologium_%28constellation%29]
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